The effect of alkali pre-treatment on formation and adsorption of silver nanoparticles on cotton surface

This study is an attempt to investigate the feasibility of alkali pre-treatment to activate surface hydroxyl groups of cellulose fibers in order to enhance the deposition efficiency of silver nanoparticles (AgNPs) onto cotton fabrics. Cotton samples were pre-treated with various alkali solutions containing different earth metal hydroxides (LiOH, NaOH, and KOH). The as-prepared samples were then treated with aqueous silver nitrate followed by reduction treatment with aqueous ascorbic acid, which caused in situ formation of AgNPs on fiber surfaces. The surface structure of the fabrics was characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) analysis, and colorimetric data. The amount of silver was measured by using inductively coupled plasma-optical emission spectrometer (ICP-OES). Antimicrobial activity was measured against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria. It was established that alkali pre-treatment had a substantial effect on the formation and adsorption of AgNPs on the fibers. Alkali pre-treated samples were homogeneously coated by AgNPs with high surface coverage. Alkali type had significant effect not only on the amount of AgNPs on the surface but also on its size. High antibacterial activity against both Gram-positive and Gram-negative strains was also demonstrated, even after 10 cycles washing.     

Various nano-silica particles affecting dyeability of poly(ethylene terephthalate)/silica nanocomposite films

Poly(ethylene terephthalate) [PET] based nanocomposites containing three differently modified silica particles were prepared by melt compounding. The influence of type of nano-silica on dispersibility, thermal and dyeing properties of the resultant nanocomposite was investigated by various analytic techniques, namely, polarized optical microscopy (POM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), reflectance spectroscopy (RS), and light fastness. Optical microscopy images illustrated that nano-silica particles tended to increase the number of spherulites in the PET matrix which were dependent on nano-silica type and content. Thermal studies of the resultant nanocomposites showed a slight decrease in the melting temperature compared to a pristine PET. Silica nanocomposites were finally dyed with a disperse dye and their reflectances were determined by the aid of reflectance spectrophotometer. Such reflectances were converted to the corresponding color coordinate values which are indicative of dyeability of such nanocomposites.